Constant speed tilting helicopter rotor head



Sept. 25, 1951 w HUNT 2,569,061

CONSTANT SPEED TIL-TING HELICOPTER ROTOR HEAD Filed Nov 15 1946 3 Sheets-Sheet l WILLIAM E. HUNT INVENTOR ATTORNEY Sept. 25, 1951 w E, HUNT CONSTANT SPEED TILTING HELICOPTER ROTOR HEAD 3 Sheets-Sheet 2 Filed Nov. 15, 1946 POWER ON ADDED POWER AUTOROTATION EXOESSIVE FLAPPlNG ROTOR STOPPED WILLIAM E. HUNT IN VENTOR ATTORNEY Sept. 25, 1951 w. E. HUNT 69 CONSTANT SPEED TIL-TING HELICOPTER ROTOR HEAD Filed Nov. 15, 1946 3 Sheets-Sheet 5 :F'ig.1Z HEVERT'YJZ BY 76M ATTORNEY Patented Sept. 25, 1-951 EZUNITED :PA; .zEiNT Eon-Tics CONSTANT. SPEED TILTING HELICOPTER moron HEAD --William 'EriiHun t lBrookly-n, N. -:Y., sassignor 420 ..United .'-;Aircraft ...C!p'cration, .East Hartford,

.Gnnmmwomoraitim of Delaware Application -Noveliiber 15, I1946,= S.erial N0. "709 ,978

'Aeclaims. (Cl. 170-.160.2 5)

This invention relatesegiinerally zrto improved controls, for helicopters, and more specifically; to @structure :providingrautomatic ipitchbcontrolg-fm the'rotor blades: operative in responseeito :torque :andto -air induced :blade movements.

A feature of'the inventien iis .therprovisionLof an :automatic pitch rcontrola operative'ito wcause :substantially a unifcrmwspeed OfiI'Oi'lfifiiQl-TDfi'bhfi This control $231180 makesitpossi- ,ble to eliminate the .itotal pitch: controls: .in'scertain ships, and control of .lift -ise-accomplished throughtmanipulation of the--throttle-:=only. In other ships, totalpitch control may beg-used in conjunction with the 'yaiutomatic pitch control, which combination of elements provides ;:addirotor blades.

.tional yfeatures .of 1 convenient tadjustment, rand trimming of theiship for: different loads.

,Another feature of-the zinventionris the;-provi- ;.sion of 1' an improved -.con;tro1 ,i-ncludi-ngsaeuniver- I isally'; pivoted, rotor head. that-eam-beztilted'withrrespect :to the :body of gthe shelicoptertto efiect directional ,control.

other features: and obj cts include lthe'sdfita'i inf1construction;andearrangementwoflparts Of'-:th8

controls and the .difterentmechanismssjtor per- .forming-;desirable-control1 fiunctionsaand-will wbe either obvious :or ;-.pointedaoutsin::,-the;'2fo1lowing zspecification and-claims.

In the drawi s, Figure ,1; is .a -side.relevationaltviewi of aarheli copter including my :zinvention;

Figure 2 is-arpartialssectionalz viewrof; arrotor :head used inpreferredij form: ofithe invention;

Figure 3 isa-partialzplaniview fsthatrform'rof the. invention shown-in; Figurezfl;

;sFigures:,4;5, .6, 17:3;ndL85fl116; agraimmaticzviews ".Of'. the preferred :form of the1':mventioneat: different phases'of operation.

.Figures 9, and 111' arevorthographicallymrojectedtviews of a:mo'dificationyof the invention:

and

1 Figures 12 l and 13 rare partial :plansand: elevational views respectively ohanothemmodification e of the invention.

Referring more i in detail totFigurei lithe'iheli- :acopter :hasa body M wwhich supports samengine 12 for turning a a drive shaft disconnected -:with

:a. reduction gear 1161whichtat:lits ilowiespeedssend rconnects with anditurnsagcrotorirhub 8 torwhich ;blades are: secured byihingesi'toirbe describedi ;below. A drive:shaft-22 connectsito thegears within the gear :lloox I6, gatsonetzendsandat zthe 0.ther end :connects with a drivermechanismrfor an auxiliary rotor 24 for counterbalancingathe trol. ';The forwardzpart' of the body In contains =1 seats; 2 6.. for occupants: and has azimuth: controls 7 iaeconnected by :links with a' tilt mechanism .32 to. be discussed :more. fully below. When a :5 'w-control stickyZB isrmoved the tilt mechanism 32 :will! be tilted" in azimuth to:tiltithe1p1ane'of"r0- rtation of the rotor'bladeslll. In'themodification shown: in Figures 1,: 2 and 3, :the rotor hub I I8 is .tilted,aand in: the othermodifications'of'the i 0 invention, reflective tilting i is obtaine'd by cycli- ;cally varying the pitch of'the rotor blades,an'd

will i'be discussed more fully 'below.

Referringtnow to Figure 2,'a drivezshaftflicon- :nects by splines sand at; lo'ck'nut' 31 withsa "yoke .115 38 having at its open endtbearin'gslfl. spider J42, is journaled in: the bearings wand ihastransverse arms .44, of which there-are two, journaled ,into :a housing of :the rotor head'l8. structuref. forms a universal joint'which :permits aeo'theyhub l8 to 'tilt .in all directions in azimuth .about' the. shaft. Thehousing 46 isprovided -with brackets, only one of which is shown-indeztailzat' 50, which bracket supports afiapping Divot 51', securing bifurcated flapping :links 'irwhich v.25; mount the rotorbladeiZ 0. Tofurthers strengthen .the'bracket -SI),'a plate 55 may beaprovidedaand secured to the upper end of: the bracket150 andaa acover-platetfiyfor the hub I 8.

;The huh I 81 may .be: tilted "around the: universal 0 "j jointby; meansofa pair of *controlrrods 58 spaced rapart which .:connect the links 30 r with the rtilt plate 32. 'The:plate32 mayibeirheld: against 1 rotation by .a scissors '60 tconnected 'between' .the zrplate 32.-and thegear box [6, Figure 1. The plate 5 :32 ;isi;rotatablyconnected with 'the hub housing 18,-which isin'tumrpivoted on apinaBO at its -other end to ears :on the flapping link 54.

' Azbracketa82 is; secured: at one end to the hub zhousing. lfiaandizat itsother end-mountse univerisalrpin "84; @The"pinu84iconnects=with:amadjustrmainrotor torquexand.proridingaidirectionnlzccneau iable .linksaamhichc .at'zthe otlier endconnects by 3 a universal pin 80 with a depending pitch control arm 90 secured to the sleeve 68. As the sleeve 60 moves back and forth relative to the pin 84 about drag pivot 64, the arm 90: will be rocked to cause the pitch of the blade 20 to be changed.

When the rotor blade 20 of Fig. 3 is rotated forward about drag pivot 64 by aerodynamic action only, in other words in autorotation, the center line, or feathering axis, of the spar I4 and blade 20 will lie substantially along a line 9| intersecting the center of the hub I8, and the drag pivot 64. When power is applied to the rotor blade 20 from the shaft 34 turned by the engine I2, the blade will be dragged backwardly until the aerodynamic and torque forces are substantially balanced by the centrifugal force. At such time, the center line, or feathering axis, of the spar I4 and the blade will be along a line 92 at some position, in the direction of rotation of the blade, behind line 9I.

Upon dragging backward of the blade, the sleeve 68 will move toward the pin 84, and the dependingarm 90 will rock around the pin 88 to cause the angle of incidence of the blade to increase. As shown in Figure 4, when power is applied to the blade 20, the blade will drag backwardly to cause a pitch increase. Figure shows the further increase in pitch of the blade upon the addition of power. When power is not applied to the blade it will move forwardly in its path of rotation in the manner described above,

and the sleeve 68 will move away from the pin 84 to rock the arm 90 in a clockwise direction to decrease the pitch of the blade 20. This condition is illustrated in Figure 6.

The linkage discussed above may also provide for aerodynamic damping of flapping motion. As the blade 20 flaps upwardly beyond a predetermined maximum degree, it is desirable that the lift of the blade be decreased so that it will return to its position in track with the other blades. As best shown in Figure '7, as the blade 20 flaps upwardly as it would upon encountering an upward gust of air, for example, the link 86 will rock about the pin 84 in a direction to cause the depending arm 90 to rotate in a clockwise direction. Such rotation will cause the pitch of the blade to be decreased. Conversely, when the blade flaps downwardly the pitch of the blade will be increased. It is to be noted that the link 86 can be adjusted to move the pivot points 84 and 88 with respect to each other. This will cause the arc traversed by the pivot point 88 to become more or less flattened to vary the degree of flapping at which automatic damping will become effective. Accordingly, with the use of the linkage, it is possible to obtain both automatic pitch control and aerodynamic damping of flapping to substantially any practicable degree.

'. Figure 8 shows the position of the rotor when it is stopped. It is to be noted that the blade has substantially zero pitch so that upon setting the rotor into operation the engine will be loaded at only a minimum, and the'rotor will not cone upwardly excessively.

Referring now to Figures 9, 10 and 11, a rotor blade I00 is connected by a flapping link I02 with a hub I04 turned by an engine, not shown. The

' blade can drag backwardly around a drag pivot I06, and flap up and down around a flapping pivot I08. Control mechanism diagrammatically indicated at I I0 comprises a non-rotating tilt plate II2, a rotating tilt plate II4 journaled thereon, a ball joint sleeve II6 upon which the plates H2 and H4 may be tilted cyclically, pitch control mechanism to rod controls II8, push-pull rod I20, a bell crank I22 mounted in a bracket I24 secured to a drive pivot I26 on the hub I04, a rockable link I28, and a depending arm I30 secured to a rotatable sleeve I32 for the blade I 00.

The operation of the link I28, the depending arm II30, and the sleeve I32 is substantially identical to that explained above in connection with the first modification of the invention. As power is applied to the blade I00, it will drag backwardly to increase its pitch. As the blade flaps upwardly in its operation its pitch will be decreased. Accordingly, the automatic total pitch control andaerodynamic damping may be identical to that discussed above.

In addition to the automatic pitch control, for the purpose of providing for trimming of the craft and to render it possible to operate more economically when flying at different altitudes or with different loads, or both, I employ total pitch control in the control mechanism IIO. As the sleeve IIB is moved up and down by the action simultaneously of the rods I I8, of which there may be three, the link I20 will be moved up and down to rock the bell crank I22 to, in turn, rock the depending arm I30 to change the pitch of the blade I00. For further details of construction of a device for controlling total pitch in such manner, reference may be had to Patent No. 2,529,635, issued November 14, 1950, to I. I. Sikorsky et al.

In the modification shown in Figures 9, l0 and 11, cyclic pitch is used with universally mounted blades only, rather than with a universally mounted head in combination with universally mounted blades. The details of such blade mounts are set forth in the above mentioned application, in which the blades change in pitch a complete cycle in each revolution of the rotor. When the control rods II8 are moved differentially, the tilt plates H2 and H4 are tilted with respect to the drive shaft I26. Accordingly, the push-pull rod or link I20 will be raised and lowered once in each revolution. Raising and lowering of the rod I20 will cause the bell crank I22 to rock cyclically and the pitch of the blades I00 will be changed cyclically accordingly. Hence it is seen that I have provided a modified structure including automatic pitch change in response to torque and aerodynamic force in combination with cyclic control, and havingtotal pitch control for trimming purposes.

Figures 12 and 13 disclose a modified arrangement of linkage similar in operation to the modifications discussed above, but in this last modification the push-pull link is used to afford aerodynamic damping upon flapping of the rotor blades, and the control mounted upon the flapping link are used, which controls may be similar in many respects to the controls disclosed in th application mentioned above.

A control mechanism 2I0 comprises a nonrotatable tilt plate 2I2 and a rotatable tilt plate 2I 4 that turns with a drive shaft 226, and control rods 2I8 which may be operated simultaneously to raise or lower a ball sleeve 2I6 and the plates 2| 2 and 2I4. The control rods 2I8 may be operated differentially to tilt the control mechanism 2I0 for obtaining cyclic pitch of a blade 200. A push-pullrod or link 220 is off-set from the axis of a flapping link 208 so that when the blade flaps upward the link 220 will cause the pitch decrease the pitch of the blade. e

The link 220 connects With'a rocker arm' 230 which turns a shaft 232 journaled at one end in a bracket 234 and at its other end to a bracket 236 carried by a blade spar 238. The shaft 232 contains a universal joint 240 in alignment with a drag pivot 242 so that as the blade 200 rotates along the drag pivot 242, the shaft 232 will not be stressed. The shaft 232 in turn rocks an arm 243 connected by a link 244 to a lever 24B fulcrumed on a bracket Z48 mounted upon the flapping link 202. The lever 246 connects by an adjustable link 250 with a depending arm 252 which is connected with the spar 238 for changing the pitch of the blade 200.

Automatic pitch control in response to torque and aerodynamic forces is obtained in this modification 'as follows:

When torque is applied to the blade 200, the spar 238 will drag backwardly. Such motion will cause movement of the spar 238 toward the bracket 248. This in turn will cause the link 244 to move to the left to rock the lever 246 in a counterclockwise direction to cause the depending arm 252 to rotate in a counterclockwise direction to increase the pitch of the blade. The movement of the blade will also cause additional rock-- ing about the link 250 so that this modification may be made extremely sensitive to small motions, if desired. It is to be understood that any suitable proportions for the link and lever. in this modification may be selected to obtain the most desirable function, and that by changing these proportions a large variation in effects is possible.

While I have shown and discussed in detail three forms of my invention, it will be understood that other modifications thereof may occur to those skilled in the art and that my invention is not limited to those forms shown and described but only by the scope of the following claims.

I claim:

1. In a helicopter, an upright drive shaft, a rotor hub universally mounted on said shaft, a rotor blade mounted on said hub for pitch changing movement having hinged connections with said hub permitting flapping and drag movements of said blade, control means for tilting said hub for directional control of the helicopter, and linkage means for effecting increase in the pitch of said blade as a result of lagging movement of the latter including a blade horn rigidly mounted on and depending from said blade, a bracket rigidly mounted on said hub, and a connecting link between said bracket and horn having pivotal connections at its opposite ends with said rigid bracket and horn respectively.

2. In a helicopter, an upright drive shaft, a rotor hub universally mounted on said shaft, a rotor blade mounted on said hub for pitch changing movement having hinged connections with said hub permitting flapping and drag movements of said blade, control means for tilting said hub for directional control of the helicopter, and a linkage means for effecting decrease in the pitch of said blade as a result of flapping movement of the latter including a rigid blade horn depending from said blade, a bracket rigidly mounted on and extending outboard from said hub alongside said blade, and a link pivotally connected at one of its ends to said rigid bracket and at its other end to said rigid blade horn.

3. In a helicopter, an upright drive shaft, a rotor hub mounted on said drive shaft for universal movement about the axis of said shaft, a flapping link having a generally horizontal hinged connection with said hub, a blade root shaft having a generally vertical hinged connection with said link, a blade mounted on said root shaft for pitch changing movements about the latter, and linkage means for effecting increase in the pitch of said blade upon upward flapping and decreasing the pitch thereof upon movement of said blade backward about said generally vertical hinge as a result of increased torque applied to said drive shaft, said means including an axially offset blade horn rigidly carried by and depending from the cuff of said blade, an arm rigidly mounted on and extended outboard from said hub and terminating adjacent the free end of said horn, and a link pivotally connecting the free ends of said rigidly mounted arm and horn.

4. In a helicopter, an upright drive shaft, a rotor hub mounted on said drive shaft, a flapping link having a generally horizontal hinged connection with said hub the axis of which intersects the axis of said drive shaft, a blade root shaft having a generally vertical hinged connection with said link at the outboard end of the latter, a blade having a cuff pivotally mounted on said root shaft for pitch changing movements about the latter, and linkage means for effecting increase in the pitch of said blade upon upward flapping and decreasing the pitch thereof upon movement of said blade backward about said generally vertical hinge as a result of increased torque applied to said drive shaft, said means including an axially ofiset blade horn rigidly mounted on and depending from said cuff, a bracket rigidly mounted on said hub and extended outboard therefrom and terminating adjacent the free end of said horn, and a link pivotally connected at its opposite ends respectively with the free ends of said rigidly mounted bracket and said rigidly mounted horn.

WILLIAM E. HUNT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,919,089 Breguet July 18, 1933 1,927,966 Vaughn Sept. 26, 1933 1,986,709 Breguet Jan. 1, 1935 2,074,342 Platt Mar. 23, 1937 2,397,154 Platt Mar. 26, 1946 2,397,489 Jenkins Apr. 2, 1946 2,410,459 Platt Nov. 5, 1946 2,432,677 Platt Dec. 16, 1947 2,440,225 Pullin i is Apr. 20. 1948 

